Cigarette filter plug



I United States Patent 113,543J69 [72] Inventors James B. Arthur;3,253,969 5/1966 Pannill, Jr., et a1. 13 l/267X John J. Osmar,Charlotte, North Carolina 2,966,157 12/1960 Touey et al. 131/269 [2]]Appl. No. 693,656 3,093,142 6/1963 Swerdloffet al.. 131/268X [22] FiledDec. 26,1967 3,131,428 5/1964 Mika l31/268UX Continuation f 50 3,224,45312/1965 Mahoney et al. 131/268 N 14 r956 abandoned, which 3,396,0738/1968 Touey et al. 131/761UX is a division of Ser. No. 265,518, p iExaminer Melvin Rein 15, 1963' abandoned- Attorneys-Leonard Horn, S. D.Murphy and William J. [45] Patented Dec. 1, 1970 Mason [73] AssigneeCelanese Corporation a corporation of Delaware [54] CIGARETTE FILTERPLUG 4 Claims Drawing Flgs' ABSTRACT: A cigarette filter plug isdescribed which is com- US. Cl. posed of a plurality of dereglsteredcrlmped cellulose ester l 1 Int. Cl. filaments the filaments extendingapproximately longltn- 01/04 A24f13/06 dinally from end to end of theplug and the plug having of Search preferably to independent filamentshaving 105, 261-269 about 4 to 40-crimps per inch. The relationshipbetween linear er filament and ercent of fiber in the filter lu fallswithin [56] References Cited she zone CDGl-l sf FIG, 1. The celluloseesteffiliments in the UNITED STATES PATENTS plug are unbonded and theplug is characterized by good firm- 3,079,978 3/1963 Cobb, Jr'., et all3 l/267X ness and resilience.

PERCENT FIBER DENIER PER FILAMENT Sheet of 2 lb 2 l4 DENIER PER FILAMENTJames B. Ar/hur John J. Osmar Sheet of 2 C: T n 26 Q James 5. 'Ar/hurJOh/i J. 05mm CIGARETTE FILTER PLUG This application is a continuationapplication of application Ser. No. 604,506 filed Nov. 14, 1966, nowabandoned which in turn is a divisional application of application Ser.No. 265,518 filed Mar. 15, 1963 now abandoned.

The present invention relatesto novel filters and more particularlynovel cigarette filter plugs.

In the filtration of smoke produced by combustion of tobacco it has beenproposed to employ crepe paper, absorbent cotton, etc. In the lastdecade the overwhelming proportion of commercially available cigarettefilters have comprised longitudinally extending crimped filaments bondedto one another at their contact points by solvation bonds. The procedurefor producing such filters involved producing a tow or untwisted bundleof several thousand continuous filaments, crimping the tow, opening thetow to deregister adjacent crimps, fluffing the opened tow to pennitsubsequent uniform X application of a plasticizer, pulling the towthrough the zones of plasticizer application and fluffing, wrapping theplasticized tow in paper, severing the wrapped tow into rods ofpredetermined length and thereafter curing the rods to effect bondingbetween adjacent filaments at their contact points.

Another object of the invention is to produce novel cigarette filterplugs.

Other objects and advantages of the invention will become apparent fromthe following detailed description and claims taken in conjunction withthe accompanying drawing wherein:

FIG. 1 is a graph identifying the novel plugs embraced by the presentinvention;

FIG. 2 is a schematic view of one apparatus for making plugs inaccordance with the present invention; and

FIG. 3 is a schematic view of an alternative apparatus for making plugsin accordance with the invention.-

In accordance with the method of making the disclosed plugs of thepresent invention, with selected tows when the opening of the tow iseffected with certain equipment the resulting deregistered tow can beformed into filters without the need for plasticization and subsequentcuring. It is even possible to eliminate the fluffing step since thereis no need to prepare the tow for uniform receipt of plasticizer;without plasticizer-applying or fluffing-apparatus the need forequipment to pull it therethrough is also overcome. Thus, in itssimplest form of rod making equipment comprises only towcrimp-deregistry equipment followed immediately by wrapping equipment.

The opening equipment must be such that there is substantially completederegistry between the crimps of adjacent filaments. Lesser deregistryresults in plugs which are too soft, difficult to wrap initially informing the rods as well as in joining the rods to tubes of tobacco inmaking filter tip cigarettes, and which do not spring back aftercompression (as between the fingers or lips during smoking) withattendant channeling of the smoke. For these same reasons the openingequipment should not operate so strongly on the tow that the crimps arepulled out and the tow is of diminished bulk; while this could becompensated for by utilizing heavier tows the resultant plugs would beso dense as to make it exceedingly uncom-' fortable to draw smokethrough the filter, i.e. its pressure drop would be too high.

One apparatus especially suited for effecting such deregistry comprisesat least one pair of cooperating surfaces.

Advantageously the surfaces are rolls adapted to rotate either by apositive drive or idly by contact with a rotating roll. Advantageouslyone roll of each set is rigid while the other has a yielding surface,e.g. steel versus rubber or synthetic elastomer and the rolls are urgedinto contact so that both rotate upon driving of but one. At least oneroll of one set is not smooth surfaced so that all filaments across thewidth of a tow passed therebetween will not be identically treated.

In one embodiment, there are provided two pairs of rolls with their nipsin horizontal or preferably vertical alinement. One roll of each pair isdriven and has a smooth rubber surface. The other surface of each pairis idly mounted and spring urged into contact with its driven mate to becaused to rotate thereby. The idle roll has a helical thread cut in itssteel surface. Advantageously the downstream driven roll is driven at asurface speed faster than that of the upstream driven roll. Thereby thetow is subjected, while being fed along a predetermined path, to adifferential gripping action between a plurality of points spaced fromone another both longitudinally and transversely of the path, so thatcertain laterally spaced sections of the tow are positively grippedrelative to other laterally spaced sections of the tow, alternating withthe said gripped sections, which are not gripped at all or are grippedat different relative points. In this manner, there is produced, as afunction of thedifferential positive gripping of the tow, a relativeshifting of adjacent filaments longitudinally of the tow, whereby thecrimps are moved out of registry with oneanother. Preferably, althoughnot necessarily, the differential gripping action is such that arelative longitudinal displacement between adjacent filaments of the towis also effected, so that the combination of two transverse filamentmovements brings about the complete opening of the tow.

By way of definition, the term gripping gripping"(or any variantthereof) is used herein to denote the confinement of the tow by twoopposed members which tightly engage the tow at its opposite faces, andthe term differential gripping is used to denote the confinement of thetow between two opposed members, as well as between sets of such opposedmembers, which have zones in which the tow is tightly engaged by themembers alternating with zones in which the tow is only loosely or notengaged by the said members. The terms include a mere one-sidedfrictional sliding engagement between the tow and a member past whichthe tow moves.

The nonsmooth surface has been described as preferably helical, thisbeing one of the easiest surfaces to produce and one of the mostsatisfactory to work with. Advantageously there are about 10 to 20threads per inch and the ridges which contact the smooth surfaces areflattened. Each grooved roll may be helically grooved in oppositedirections from its center to its ends, or may be continuously helicallygrooved in either direction across the roll. Where several helical rollscontact the tow in sequence the arrangement of grooves can be alike onsuccessive rolls or in opposite directions on successive rolls orgrooved from the center to the end of opposite directions on successiverolls.

While helical threads are preferred the surfaces of the nonsmooth rollsmay be formed of circular or cylindrical ridges or of elliptical orundulating rings. It can even comprise a checkerboard of alternatedraised and lowered surfaces, or it can comprise spaced projections forpinching the tow against the cooperating surface.

It has been found useful to employ two sets of rolls whose nips areabout 10 to 50 inches and preferably about 15 to 25 inches apart. Whilethe tow path in moving between rolls sets may be inclined as much as 45to the vertical, advantageously its inclination is less than about 25and preferably it is substantially vertical. The profiled or nonsmoothroll of each pair is advantageously urged against the smooth roll with aforce of about 5 to 30 or more and preferably about 5 to 15 pounds perlinear inch of contact between the rolls. Lower forces may result inexcessive slippage where the tow is not extremely heavy, and higherforces may result in injury to the roll surfaces and to tow passingtherebetween.

The first or rear driven roll pulls the tow along from a bale or ballwarp over bars which straighten it out slightly and control the sidewisemotion. The surface speed of the rear driven roll generally ranges fromabout 50 to percent of the speed at which the the opened tow isultimately received by the garniture and fed to the belt of a cigarettewrapping machine by which it is formed into filter tips; preferably thespeed is about 75 to 100 percent of the belt speed, i.e. the tow 'in thefilter tips is substantially as long as in the crimped unopened state.The front, second or downstream" driven roll operates at a speedvaryingfrom about I20 to 300 percent and preferably from about to 225percent of .the upstream product uniformity special apparatus isprovided for handling the tow between the grooved rolls and the bale inwhich it is shipped. Because of the tight compression within the balethe tow band width will vary as well as the weight per unit length andthe ease of withdrawal from the bale. Further variations result as thetow position changes vertically and laterally within the bale. As thebale is used up, there is a change in the length of tow from the top ofthe bale to the overhead guides normally used; this change in lengtheffects a change in tension and thus in weight per unit length. Suchvariations are overcome by introducing a small amount of pretensioningupstream of the grooved rolls. Specifically, the tow from the bale iswithdrawn upwardly and caused to pass over a substantially straightguide surface which causes it to be flattened. The guide surface, whichis preferably a horizontal rod positioned about 4 feet over the bale,allows shifting of. the tow band laterally therealong as the tow iswithdrawn first from one side of the bale and then from the other side.As a consequence jerking and plucking of the band are eliminated. Thelightly tensioned tow is now of substantially constant width and weightper unit length and passes horizontally through an air spreader in whichits width is increased several fold. The wide band may be passed overseveral additional direction-changing guide bars before reaching thegrooved rolls. While these bars do not affect any deregistry or opening,they do serve to pretension the band uniformly so that it will be in thebest condition for being operated upon by the grooved rolls. 7

Even with this equipment, however, only a fraction of the towscommercially available will produce satisfactory filter plugs in theabsence of plasticizer. The tow is preferably composed of a plurality ofcrimped continuous filaments of an organic derivative of cellulose, e.g.esters or ethers of cellulose such as cellulose acetate, cellulosepropionate and'cellulose acetate propionate, highly esterified cellulosecontaining less than 0.29 free hydroxyl groups per anhydroglucose unitsuch as cellulose triacetate, and the like. Other filamentary materialssuch as rayon (regenerated cellulose) lineary superpolyamides such asnylon-6 and nylon-66, linear polyesters, and

polymers and copolymers of vinylidene compounds such as number ofcrimpsper inch in the tow can range up to about 30- 40, but preferablyaverages between about 4 and 25, e.g. 8 to l2 computed on an inch ofstraightened tow. The percent tensioned length-contracted lengthcontracted length X 100 crimp, i.e.

ranges from about 50 to 200 percent and preferably from about 75 to 150percent.

In addition to meeting the foregoing requirements, the denier perfilament should bear a particular relationship to the proportion of theplug or filter rod apparent volume which is actually air space ratherthan being occupied by fiber. This relationship is illustratedgraphically in FIG. l of the drawing which was arrived at from dateobtained with secondary cellulose acetate tows formed into filter rodsof 17 mm. length and 25 mm. circumference, the individual filamentsbeing Y- shaped in cross section. The topmost limit of the chartrepresents aplug of solid acetate, i.e. 100 percent fiber, while thelowermost limit represents no acetate or 0 percent fiber. The zoneA,C,D,E,F,G,H encloses those plugs falling within the present invention.Above this zone even at low percentages of fiber the pressure drop, i.e.force required to draw smoke therethrough at the rate of U5 cc. persecond, will be unduly high, e.g. in excess of about 90 mm. of water.Below this zone filter plugs will be so soft that often there will bewrinkles and dimples in the encircling paper. Moreover, there may be solittle resistance that wrapping may be rendered difficult. To the rightof the zone the individual filament denier is so great that there isrelatively little filament surface available for filtration, thefilaments are relatively coarse and the overall effect if little morethan an empty tube. To the left of the zone the rods are quite soft evenwhen they contain enough fiber to give effective filtration.

The whole enclosed zone is not equally advantageous. The area CDGl-lrepresents the preferred rods and the area HKLM the most preferred rods,from the standpoints of performance, ease of production, firmness, andresilience. The combination of firmness with resilience is mostimportant in unbonded plugs. In actual use filters are compressed anddistorted out of shape. While the paper wrapper may rebound, often thefilaments do not so that .channels are formed between the paper and theperiphery of the filaments making up the plug. Moreover, pressure on abonded filters causes only the peripheral filaments near the point ofpressure application to be displaced so that smoke channelspreferentially through the remainder of the filter; with the novelplugs, the pressure is transmitted so that many filaments adjust theirpositions and all are effective in filtration. Consequently, with bondedplugs the theoretical smoke removal efficiencies determined in thelaboratory ,will frequently not be realized in practice due to thesmokes bypassing the filter. When the filaments are independent, i.e.unbonded, they are free to bounce back, being unrestrained by adhesivebonds. Consequently the performance of the most preferred unbonded plugsof the present invention approach the theoretical values of laboratorytests. This is further evidenced by carefully longitudinally slittingthe paper wrappers of bonded and unbonded plugs. The wrapper oftheunbonded plugs flies open under. the force of the filament and thecross-sectional area of the filament bundle increases by at least about20 percent and often more than 35 percent. With bonded plugs, thesevered paper edges open only slightly and the cross-sectional area ofthe filament bundle is substantially unchanged.

Another way of establishing this is by testing the plugs forcompressibility. Compressibility, the inverse of firmness, is measuredby permitting a weighted knife edge to rest transversely of the plug for10 seconds; the extent to which the plug returns to its originaldiameter is an index of firmness. After removing a -knife edge loadingof 4-ounces the preferred novel plugs return rapidly to a diameter of atleast about percent and preferably at least about percent of theiroriginal diameters, both faster and higher than for correspondingplasticized plugs.

The preferred plugs usually exhibit a smoke removal efficiency of atleast about 20 percent and preferably at least about 30 percent,determined as follows: 12 puffs of 35 cc., i.e. 2 seconds of puffing aredrawn from a lit cigarette through the filter and through a trap havingon its bottom a sintered glass disk. 2 grams of sifted alpha celluloseare placed on the disk, producing a pressure drop of about 5 centimetersof water. The trap is immersed halfway in a dry ice-acetone bath. Theformula for the smoke removal efficiency is as follows: Percentefficiency Increase in Weight of Filter Increase in Weight of FilterPlus Trap The foregoing evaluations were made with Y cross sectionfilaments, which exhibit a somewhat greater firmness and smoke removalefficiency than regular cross section filaments at any particularpercent fiber in FIG. 1. The effect is that the lower boundaries of theenclosed zones of FIG. 1 will have to be raised somewhat for regularcross section fibers. Alternatively, the paper wrapper could be mademore firm by being built up. Similarly, the upper limit could be raisedsomewhat by employing filter plugs less than 17 mm. long thereby todiminish the pressure drop. Other cross sections will give resultsapproximately intermediate Y and regular. The curves were determinedwith secondary cellulose acetate having a specific gravity-of 1.3;different fibers will result in a small displacement of the curvesalthough their shapes will be the same.

FIG. 2 shows a suitable apparatus for producing the novel plugs. In FIG.2 the tow 1 1 is taken from a bale 12 passing over an overheadhorizontal bar 13. The tow direction is thereby diverted to thehorizontal, the tow entering air spreader 14 wherein its width isincreased several fold. The tow 11 is pretensioned by direction'changingbars 15, 16, 17 and 18 but the crimp is still visible with the crimps inregistry between adjacent filaments across the tow band. The tow 11 nextpasses between helically grooved idle steel roll 19 and driven rubberroll 20 and then between similar steel and rubber rolls 21, 22, wherebyopening is completed. The opened tow passes over pin 23 which ensuresits removal from the rolls and the tow is taken up in the garnituretrumpet 24 of a cigarette making machine 25 wherein it is wrapped inpaper and discharged as a continuous plug 26 which is severed by a knife27 into short plugs 28 of predetermined length.

FIG. 3 shows an alternate apparatus wherein the tow 11 leaving pin ispassed about another pin 29 which directs it vertically downward betweenthe nips of rolls 19, and 21, 22 (now positioned for a vertical towpath). The opened tow now passes directly to garniture trumpet 24 evenwithout an intermediate separator pin.

The invention will be described further in the following illustrativeexamples.

EXAMPLES 1T0 9 Secondary cellulose acetate tows having about 12 crimpsper inch and 100 percent crimp are passed throughthe apparatus of FIG. 2wherein the nip of rolls 21, 22 is 20 inches from that of rolls 19, 20,roll 22 operating at 1.7 times the speed of roll 20. Rolls 19 and 21 aremade of steel having cut therein a helical thread of 14 turns per inch,Each. turn has a 60 apex angle at its base and a flat 0.017 inch wide.Rolls 19 60 and 21 are urged against rolls 20, 22 with a spring force of10 pounds per linear inch of contact.

In the following runs the indicated results are achieved, the examplesbeing indicated in FIG. 1:

Dcnler Total Cross Percent Pressure Percent Ex per Ill. denier sectionfiber drop, smoke X1, 000 mm. 1120 removal efficiency 6 EXAMPLES 10-55Total denier X1,000

Denier per filament Zone 01 figure 1 Cross Percent section b Example erR= Regular. 1==H, K, L, M; 2 F, G.

It is to be understood that the foregoing detailed description is merelygiven by way of illustration and that many variations may be madetherein without departing from the spirit of the invention.

We claim:

1. A cigarette filter plug having a pressure drop of less than about 90millimeters of water and an acceptable smoke removal efficiency andfirmness composed of a bundle of independently crimped cellulose esterfilaments each extending approximately longitudinally from end to end ofsaid plug, said filaments being free of interfilamentary bonding, theplot of denier per filament versus percent of fiber for said plugfalling within the zone ACDEFGI-I of FIG. 1, said bundle beingsurrounded and compressed by a paper wrapper, the removal of whichresults in an increased in the cross-sectional area of said bundle by atleast 20 percent. 7

2. A plug according to claim 1 wherein said filaments are comprised ofcellulose acetate.

3. A plug according to claim 1 wherein at least some of said filamentsare Y-shaped in cross section.

4. A cigarette filter having a pressure drop of less than 90 millimetersof water and an acceptable smoke removal efficiency and firmnesscomposed o a bundle of about 5,000-

33,000 independent cellulose ester filaments having about 4-40 per inchwith the crimps of adjacent filaments being out of registry, saidfilaments extending approximately longitudinally from end to end of saidplug, said filaments being free of interfilamentary bonding, the plot ofdenier per filament versus percent fiber for said plug zone within thezone CDGl-I of FIG. 1, said bundle being surrounded and compressed by apaper wrapper, the compressibility of said plug being such that thediameter thereof will return to at least about percent of the originaldiameter after resting a knife edge transversely on said plug for 10seconds under a load of 4 ounces.

Patent No.

UNITED STATES PATENT OFFICE Dated December 1, 1970 n fl LJamqs B. Arthurand John J. Osmar It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1,

Column 2, "gripping".

Column 2,

Column 2,

Column 3,

Column 6,

line

line

line

line

line

line

line

line

line

line

line

73, "alinement" should read "alignment".

22, 'gripping" gripping" should read 30, "in-" should read "ex".

43 "of" should read "in".

46, "aerylonitrile" should read "acrylo- 3, "date" shoudid read "data".

21, "if" should read "is".

33, "filters" should read "filter".

58, "increased" should read "increase".

68, after"440" should be inserted crimp 72, after "zone" should beinserted "fall Signed and sealed this 11 th day of May 1971 (SEAL)Attest:

EDWARD M.FIETCHER,JR. Attesting Officer WILLIAM E. SCHUYLER, JRCommissioner of Patents

